Five of your friends took a week-long vacation. You know that in this group not every one is a perfect truth-teller, and if someone is a liar, he is a consistent liar.
Since they know you are an avid puzzle-solver, they decided that each day one of them will send you a message, regarding their attitude towards truth-telling.
The sequence of their messages is as follows :

Monday: There is exactly one liar among us.
Tuesday: I am not a liar.
Wednesday: There are exactly 3 liars among us.
Thursday: There are exactly 5 liars among us.
Friday: There are exactly 4 liars among us.

On Saturday you were asked:
Were you able to reason out how many of us are LIARS?